Sensitivity of the cancer screening items in Japan’s Comprehensive Survey of Living Conditions: a medical record-linked cross-sectional validation study

Background In Japan, national estimates of cancer screening utilization rely primarily on self-reported data from the Comprehensive Survey of Living Conditions (CSLC). However, the validity of the CSLC cancer screening items introduced in 2013 has not been verified against objective screening records. The study aimed to validate the cancer screening items used in Japan’s CSLC by comparing self-reported screening histories with medical records. Methods We conducted a cross-sectional validation study by mailing a questionnaire replicating the CSLC cancer screening items to randomly selected individuals with known screening histories at a large screening center. Returned questionnaires were linked to electronic medical records. The primary outcome was the sensitivity of the questionnaire items for gastric and breast cancer screening within a 2-year window (fiscal years [FY] 2022–2023). Exploratory analyses assessed colorectal cancer screening within a 1-year window and cervical cancer screening within a 2-year window. To evaluate the effects of survey timing (late FY2024), we conducted a sensitivity analysis that expanded the medical record window to include screenings performed in early FY2024. Results The questionnaire was mailed to 4,000 individuals, of whom 1,151 were included in the analysis. The sensitivity of the questionnaire was 96.1% for gastric cancer screening (318/331) and 95.8% for breast cancer screening (276/288). Similarly, the sensitivity was high for colorectal (93.6%) and cervical cancer screening (96.3%). The sensitivity estimates changed minimally when early FY2024 examinations were included. Other crude agreement measures, such as specificity, were not interpretable as classification accuracy parameters because screenings conducted outside the center were unobservable. Conclusions The CSLC cancer screening items demonstrated high sensitivity, indicating that individuals who were recently screened generally reported their participation accurately. However, given Japan’s likely moderate true uptake, even modest shortfalls in specificity could inflate the national survey–based estimates. Improving questionnaire clarity and developing integrated screening registries can enhance the accuracy of population-level monitoring.